Hiring practices are not, cannot, be based on background, due to time constraints of the hiring process. It is not possible to know a person's background, though you could certainly get some idea of it given enough time, perspective alone would prevent you from understanding it as they do. In fact, hiring is based almost entirely on the prejudices of the person(s) making the hiring decision. These days, publicly traded companies are incentivized through market forces (blackrock, ESG scoring) to be prejudiced against certain groups.
If you're looking for a faith-based interpretation of the meaning of words, good, bad, or otherwise, you'll need to extend some faith in the existing meaning first.
I'm not going to defend an opinion that I haven't given, such as that the death penalty should be given to a person based on their sexual orientation. I will, however, defend the notion that every person's opinion holds valuable information and perspective. You cannot argue on principle that diversity is a good thing while simultaneously arguing that it can be a bad thing. This is an obvious contradiction. It changes the meaning of the argument from "we've discovered a fundamental truth" to "we'd like you to act a certain way" and that glosses over the outstanding implicit request, by the existence of a status quo, for you to act a certain way.
If the demand is to act a certain way, it’s only that the demand is to accept others who are different in a way that doesn’t actually harm anyone and foster an environment where no one person is unreasonably limited based on factors like being black or being a parent through thoughtless setup of the working environment.
The diversity of thought thing is always strange to me because it implies the only diversity of thought that matters is the thought to discriminate against others or the thought to put one’s head in the sand and ignore implicit discriminatory factors. Notice you totally ignored that the professor could’ve just written about accessibility, but the professor implicitly apparently does not consider accessible labs to be merit-based or something, because he argues the only solution is to sue since DEI is so against his meritocracy position.
The paradox is about unlimited tolerance, and the specific intolerance which aims to remove the liberty of thought. A society can (and should) harbor any kind of tolerance and intolerance, but must draw a line where forces grow which plan to remove this liberty, because then the tolerance ends anyway. But if you start becoming intolerant for any topic and reason, then you've already lost the tolerance.
Moderation (in the sense of temperance) as a meta-ethical principle has an exceedingly long pedigree, starting with Aristotle in the Nicomachean Ethics. Every virtue he describes is a mean between two extremes; courage lies between cowardice and recklessness, for example.
TL;DR: Every virtue has a “oops you went too far” failure mode, this doesn’t make it “self-contradictory”.